This disclosure relates generally to emulsion water repellent compositions, including such compositions for use in conjunction with wood preservatives containing, for example, cupric-ammonia, cupric-amine, cupric-ammonia-amine complexes, quaternary ammonium compounds, or other systems. For example, the emulsion water repellent compositions are useful in Alkaline Copper-Quaternary ammonium (ACQ) preservative systems
The following characterizations of certain patents and publications are provided for the convenience of the reader. No admission is made that the patents or publications are prior art, are material, or are accurate, or that the characterizations provided here can be relied upon to supplement the disclosures of the patents or publications, which speak for themselves.
Hydrocarbon emulsions have been used together with wood preservatives to impart water repellency and other benefits to the treated wood. U.S. Pat. No. 3,832,463 describes wax emulsions for wood preservatives containing hexavalent chromium. The main advantage asserted in that patent is said to be good compatibility with the preservative. Disadvantages are said to include the use of a hydrocarbon solvent which contributes to volatile organic compounds (VOC) and high cost, and possible poor shear stability.
U.S. Pat. No. 4,323,602 describes a process for making a ready-to-dilute water repellent and preservative composition for wood treatment. The composition of the paraffin wax emulsion used for the process is not disclosed or defined.
U.S. Pat. No. 6,274,199 describes water repellent compositions and processes for treating wood with water repellents and preservatives in a one-step processes. The patent indicates that it discloses a process and water repellent emulsion, which is stable under the process conditions, for the deep treatment of relatively refractory wood species. The emulsion can comprise:                (i) about 30–80 wt. % water;        (ii) about 10–50 wt. % of a hydrocarbon wax;        (iii) about 0.5–20 wt. % of at least one nonionic surfactant;        (iv) about 0–10 wt. % of an anionic surfactant;        (v) about 0–10 wt. % of an amphoteric surfactant; and        (vi) about 0–30 wt. % of an oil.Example 1 of the '199 Patent describes a formulation prepared from the following ingredients:        
Nonylphenoxypoly (ethyleneoxy) ethanol 3.89 wt. %(100 moles of ethylene oxide)Nonylphenoxypoly (ethyleneoxy) ethanol 1.85 wt. %(15 moles of ethylene oxide)Sodium dodecylbenzenesulfonate 0.44 wt. %Slack wax25.00 wt. %Neutral Oil 7.50 wt. %Water61.32 wt. %
Organic acids solubilized in ammonia are described in U.S. Pat. No. 2,768,910 to improve water repellency and other physical properties of the treated wood. U.S. Pat. No. 3,945,835 states that ammonia solubilized organic acids can be used together with ammonia solubilized copper and zinc compounds to impart decay resistance and water repellency. Similarly, WO87/06177 describes the use of ammoniacal rosin solutions for wood treatment. The main disadvantages of using organic acid ammonium salts as water repellents are relative ineffectiveness and poor handling characteristics.
U.S. Pat. No. 4,681,910 discloses water repellent coating compositions containing latex and wax emulsions. The surfactant selection for the wax emulsions is not indicated to be critical. German Patent 2,415,843 disclosed a water repellent impregnating agent comprised of paraffin wax, a fatty acid, and beeswax for wood and other cellulosic materials.
The preparation of hydrocarbon emulsions using nonionic, anionic, cationic, or amphoteric surfactants or their mixtures is a well-known art in the field of surfactant and emulsion science. The book “Emulsions and Solubilization” by K. Shinoda and S. Friberg, Wiley-Interscience, 1986, states that the optimal HLB of nonionic surfactants for paraffin wax emulsions is 10. In U.S. Pat. No. 3,382,463, the desired HLB is said to be 7–11. Salts of various fatty acids, commonly know as soaps, are commonly used as inexpensive emulsifiers for wax emulsion water repellents for the wood composite board industry.
Other patents that may have some relevance are U.S. Pat. Nos. 4,465,613 and 4,497,919.
When wax emulsions were prepared according to well-known emulsion knowledge, it was discovered that while stable in freshly prepared alkaline copper preservative solutions, the emulsions were rapidly damaged after consecutive charges of wood treatment.